Evaluation of buoyancy dynamics in the early ontogenesis of climbing perch Anabas testudineus (Anabantidae)

Abstract

The paper puts forward a new approach to estimation of buoyancy of hydrobionts using dispersion of various densities. The technique was applied to evaluate buoyancy variations in climbing perch Anabas testudineus at its early ontogeny. It was found that positive buoyancy characteristic of eggs and early stage larvae does not remain longer than the first eighty hours of development. Besides, this period is marked by significant fluctuations in buoyancy. The maximum buoyancy was recorded at the time of hatching of the embryos, which occurs at the age of approximately thirty hours. At ninety hours the buoyancy of larvae becomes negative. Later, it goes up somewhat, and the individual differences become more important in its dynamics pattern. Some individuals are neutrally buoyant, though no return to positive buoyancy was observed. The estimates obtained by the author create a foundation for further morphofunctional analysis of the hydrostatically significant structures in the early development of the climbing perch.